The problem seems to be the absence of types in Perl: if DiveVal encounters a number, it creates an array for you, not a hash: 
$ perl -MData::Dumper -MData::Diver=DiveVal -E 'DiveVal($x = {}, qw(1 
+2 3)); say Dumper $x'
$VAR1 = {
          '1' => [
                   undef,
                   undef,
                   [
                     undef,
                     undef,
                     undef,
                     undef
                   ]
                 ]
        };

[download]

BTW, I had to rewrite your code to be able to understand what it does: 

#!/usr/bin/perl
use warnings;
use strict;

use File::Find;
use Data::Dumper;
use Data::Diver qw (DiveVal);

my @extracted = <DATA>;

push @extracted, 'end';


my @currentpath = ();
my $structure = {};

for my $i (0 .. $#extracted) {
    my @list  = split /;/, $extracted[$i];
    my @list2 = split /;/, $extracted[$i+1];
    if ($list2[0] eq 'end') {
        last
    }

    if ($list2[0] gt $list[0]) {
        push @currentpath, $list[1];

    } else {
        my @req = (@currentpath, $list[1], 'required');
        DiveVal($structure, @req) = $list[3];
        pop @currentpath if $list2[0] lt $list[0];
    }
}

print Dumper($structure);

[download]

Update: See Re^3: Parsing a dataset into an arbitrary sized hash of hashes on how to fix the problem (line 28 of my code).

لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

In reply to Re: Parsing a dataset into an arbitrary sized hash of hashes by choroba
in thread Parsing a dataset into an arbitrary sized hash of hashes by DunLidjun

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